This proposed research seeks to determine the immunological significance of autologous erythrocyte rosette-forming cells (A-RFC). We will examine the participation of these self-recognizing lymphoid cells in normal immune responses and their role as potential mediators of autoreactivity. Specific aims will be 1) to characterize the functional properties of A-RFC and their role in normal as well as autoimmune responses, and 3) to assess the influence of the thymus and thymic humoral factors on the development and activity of A-RFC. Autologous rosette formation provides an excellent model for examining fundamental cell-cell interactions in the immune system, and these studies will add to our understanding of the basic mechanisms of lymphocyte activation, autoreactivity, and the role of the immune system in control of malignant states.